A hybrid drilling process of multi material stacks with one shot drilling recently emerge as an economical and time efficient method in aerospace industry. Even though the comprehensive experience and knowledge is available for the cutting parameters of composites and metals alone, significant gap exist for the hybrid drilling parameters. Determination of these parameters such as feed rate, spindle speed and pecking depth has vital importance so as to provide a robust and optimal process to ensure dimensionally high quality, burr and delamination free holes.
Main challenge of hybrid drilling operation is to obtain required hole diameter with adequate homogeneity and repeatability. In this study, effect of cutting parameters on dimensional hole quality was investigated. In addition to the hole diameter tolerances, CFRP hole enlargement phenomena which is encountered as a specific drawback of metal-exit stack configurations is also addressed within the scope of this study.
Statistical evaluation of hole quality was conducted with calculation of process capability (Cp). Effect of different cutting parameters was compared with respect to these quality variables and optimum parameter set was acquired. In order to demonstrate the effect of cutting parameters on CFRP erosion tendency, number of excessively out of tolerance holes are used and corresponding chip characteristics are evaluated.
This paper presents the results for individual contributions of drilling parameters to the hole quality as well as optimum combination of these parameters specific to given stacking configuration.
This publication summarizes a part of TAI’s research and activities within the context of LOCOMACHS Project funded by EC 7th Framework Program.